In the field of thermoplastic injection molding, thermal regulation is critical for efficient production. Typically, plastic resin must be heated to a temperature where it flows freely as a liquid. The liquid plastic is then injected into a pre-shaped mold. When the mold is cooled, the plastic solidifies in the shape of the mold and the part is ejected. Thermoplastic materials have the tendency to stick to hot surfaces in the mold. Good thermal regulation reduces cycle times, prevent sticking, and aids in part ejection. Water is most commonly used to cool or heat the mold apparatus, although other fluids may be utilized.
An object of this invention is to provide a thermal regulating mechanism for injection molds, particularly heterocavity systems. A heterocavity injection mold machine has the ability to utilize a variety of different molds during operation. This permits operators to efficiently produce output for a plurality of clients. In addition, the heterocavity system allows the owners of different molds to share in the costs of the production run. Heterocavity systems provide significant cost and production benefits to the injection mold business. However, in heterocavity systems it is often necessary to change one or more molds used in the machine between runs. By minimizing the time consumed during these changeover periods, greater overall efficiency can be achieved.
A further object of this invention is to provide a quick-change feature for heterocavity mold system which utilize a variety of locking-key mechanisms to secure each individual mold within the mold base. In certain locking-key arrangements, even though only one mold may require changing before a production run, every mold is unlocked in the process. Although the other molds may stay in place within the mold base, they are not sufficiently secured to prevent leakage of the cooling fluid that circulates throughout the mold apparatus. Furthermore, new locking mechanisms may rely on the actual compression of the "A" and "B" plates during the molding process to form a tight fluid seal. However, while the "A" and "B" plates are separated, the individual molds are not completely rigid within the mold base, thereby causing some leakage of the cooling fluid.
Current systems such as that described in U.S. Pat. Nos. 5,647,114 and 4,828,479 to Pleasant ('114 and '479 patents) provide a circulation channel for fluid to cool or heat an injection mold assembly. However, fluid must be drawn out of the apparatus before the molds are changed. This delay slows down the production cycle of current molding systems which routinely swap various molds according to production needs.
Consequently, there is a need in the art for a water jacket apparatus which maintains the fluid barrier during mold changes, yet provides the requisite thermal regulating abilities for injection mold systems.
There is a further need in the art for a mold interface which provides a secure fluid inlet and outlet channels for fluid circulation within the mold itself.